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Introduction to Molluscs

Shells consists mainly of calcium carbonate and a protein called conchin. They are the external skeleton of the Mollusca, a group (phylum) of animals comprising over 200,000 different species! Their immense diversity makes the Mollusca the second biggest phylum in the animal kingdom, after the Arthropoda (Spiders, Crustaceans, Insects).

This specialized set of lessons will give an insight to the fascinating world of the molluscs and their intriguing shells, their many uses as food, in medical and biological science, and even as currency. How an army got defeated by a mussel, and how a small snail can kill a man with its venomous sting, and also, how somebody went to jail for stealing a seashell - all these are interesting aspects of this journey through the phylum Mollusca.


Molluscs live in all climates and habitats, including the Antarctic, the Sahara, and the volcanic vents of the deep sea. They play a key role in all terrestrial and marine habitats and food chains. Their great diversity and wide distribution make their occurrence an indicator for multiple habitat factors. Changes in the molluscan fauna reflect changes in their habitats. Therefore, the study of molluscs and their shells (Malacology) is a science that addresses threats to worldwide biotopes in times of over-fishing, deforestation, and climate change. Become part of a movement to observe, conserve, and help educate others, to save our world's natural ressources we all depend on.

There are several classes of molluscs, of which these three are the most important:

Gastropods have a single (univalve) shell that is usually coiled. This class comprises the majority of molluscan species. Gastropods live on the land, in trees or even deserts, in freshwater, in all oceans and depths. They feed on almost anything: plants, algae, sponges, worms, other molluscs, and some even suck the blood of sleeping fish. The famous cone snails use poisonous syringe-like needles to hunt fish, worms, or other gastropods.

The Gastropods portrayed in the cards are:
Australian Trumpet,  Banded Dye Snail,  Carrier Shell,  Chinese Slit Shell,  Giant Agate Snail,  Glory of the Sea,  Green Turban,  Harp Snail,  Indian Chank,  Lightening Whelk,  Living Jewel,  Manus Tree Snail,  Matchless Chimera,  Midas Abalone,  Money Cowry,  Moon Snail,  Purple Snail,  Queen Conch,  Red Helmet Shell,  Scaly Foot Snail,  Spider Conch,  Textile Cone,  Tiger Cowry,  Triton's Trumpet,  True Wentletrap,  Vampire Snail, ans the  Venus Comb.

Bivalves (e.g. mussels, scallops, clams, and oysters) are characterized by a shell that consists of two valves. In some cases, the animal forms a long tube. Bivalves have no head, but some species have eyes. Usually they live attached to the substrate, but some species can actively swim or push themselves forward with a muscular foot. Most bivalves are filter feeders, but some have algae embedded in their tissue allowing them to use the sunlight for photosynthesis, and others feed on wood, sinking ships and eroding dikes.

The Bivalves portrayed in the cards are:
Edible Mussels,
Fatmucket, Giant Clam, Heart Cockle, Pearl Oyster, Pilgrim's Scallop, Shipworm, and the Thorny Oyster.

Cephalopods (e.g. squids and octopus) are predators of fish and crustaceans. The giant squid is the largest of all mollusks, attaining a length of 50 ft and a weight of 600 lb. Only one group, the nautilids, have a visible external shell, an the cards portray the Chambered Nautilus.


By the information given on the cards, lot of basic biological knowledge will be coveyed. They work best with "shells in hands".

Download the full set of ID-cards (21 MB)

Samples from the ID-cards

Compiled by Dr. Felix Lorenz, Kevin and David Monsecour, Louie Rundo, and Dr. Michael A. Mont © Molluscan Science Foundation, Inc. 2022